Doctors have long believed that disabling autistic disorders last a lifetime, but a new study has found that complete recovery is a possibility.

The study, on January 16 2013 by the Journal of Child Psychology and Psychiatry, is the largest to date of evidence that some children who exhibit signature symptoms of the autism disorder recover completely. Such extraordinary cases are likely to alter the way that scientists and parents think and talk about autism, experts said.

However, researchers cautioned against false hope. The findings suggest that the so-called autism spectrum contains a small but significant group who make big improvements in behavioral therapy for unknown, perhaps biological reasons, but that most children show much smaller gains. Doctors have no way to predict which children will do well.

The new study should put some of that skepticism to rest.

“This is the first solid science to address this question of possible recovery, and I think it has big implications,” said Sally Ozonoff of the MIND Institute at the University of California, Davis, who was an unbiased independent party not involved in the research. “I know many of us as would rather have had our tooth pulled than use the word ‘recover,’ it was so unscientific. Now we can use it, though I think we need to stress that it’s not common.”

She and other experts said the findings strongly supported the value of early diagnosis and treatment. In 1987, when the pioneering autism researcher of Applied Behavioral Analysis, O. Ivar Lovaas, reported that 47 percent of children with the diagnosis showed full recovery after undergoing a therapy he had devised. This therapy, a behavioral approach in which increments of learned skills garner small rewards, is the basis for the most effective approach used today; still, many were skeptical and questioned his definition of recovery.

In this study, a team led by Deborah Fein of the University of Connecticut at Storrs recruited 34 people who had been diagnosed before the age of 5 and no longer had any symptoms. They ranged in age from 8 to 21 years old and early in their development were in the higher-than-average range of the autism spectrum. The team conducted extensive testing of its own, including interviews with parents in some cases, to gauge current social and communication skills. On measures of social and communication skills, the recovered group scored significantly better than 44 peers who had a diagnosis of high-functioning autism or Asperger’s syndrome.

Dr. Fein emphasized the importance of behavioral therapy. “These people did not just grow out of their autism,” she said. “I have been treating children for 40 years and never seen improvements like this unless therapists and parents put in years of work.”

The team plans further research to learn more about those who are able to recover. No one knows which ingredients or therapies are most effective, if any, or if there are patterns of behavior or biological markers that predict such success. That, because of this new study, is about to change.